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Aerosol volatility and enthalpy of sublimation of carboxylic acids.

Artikel i vetenskaplig tidskrift
Författare Kent Salo
Åsa M. Jonsson
Patrik U Andersson
Mattias Hallquist
Publicerad i The journal of physical chemistry. A
Volym 114
Nummer/häfte 13
Sidor 4586-94
ISSN 1520-5215
Publiceringsår 2010
Publicerad vid Institutionen för kemi
Sidor 4586-94
Språk en
Länkar dx.doi.org/10.1021/jp910105h
Ämnesord Aerosols, analysis, chemistry, Air Pollutants, analysis, chemistry, Atmosphere, chemistry, Dicarboxylic Acids, analysis, chemistry, Fatty Acids, analysis, chemistry, Molecular Structure, Pimelic Acids, analysis, chemistry, Thermodynamics, Volatilization
Ämneskategorier Kemi

Sammanfattning

The enthalpy of sublimation has been determined for nine carboxylic acids, two cyclic (pinonic and pinic acid) and seven straight-chain dicarboxylic acids (C(4) to C(10)). The enthalpy of sublimation was determined from volatility measurements of nano aerosol particles using a volatility tandem differential mobility analyzer (VTDMA) set-up. Compared to the previous use of a VTDMA, this novel method gives enthalpy of sublimation determined over an extended temperature range (DeltaT approximately 40 K). The determined enthalpy of sublimation for the straight-chain dicarboxylic acids ranged from 96 to 161 kJ mol(-1), and the calculated vapor pressures at 298 K are in the range of 10(-6)-10(-3) Pa. These values indicate that dicarboxylic acids can take part in gas-to-particle partitioning at ambient conditions and may contribute to atmospheric nucleation, even though homogeneous nucleation is unlikely. To obtain consistent results, some experimental complications in producing nanosized crystalline aerosol particles were addressed. It was demonstrated that pinonic acid "used as received" needed a further purification step before being suspended as a nanoparticle aerosol. Furthermore, it was noted from distinct differences in thermal properties that aerosols generated from pimelic acid solutions gave two types of particles. These two types were attributed to crystalline and amorphous configurations, and based on measured thermal properties, the enthalpy of vaporization was 127 kJ mol(-1) and that of sublimation was 161 kJ mol(-1). This paper describes a new method that is complementary to other similar methods and provides an extension of existing experimental data on physical properties of atmospherically relevant compounds.

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